Theodosian Walls of Constantinople

Timeline

1. 413–439Western land walls of Constantinople · ConstantinopleUnder the direction of chancellor Anthemius, a main wall 12 meters high and about 6 meters thick was built, with a lower outer wall and a moat up to 20 meters wide added outside, forming a defense in depth.
2. 626–1422Constantinople · Byzantine EmpireThe walls withstood repeated sieges by Avars, Arabs, Bulgarians, and crusaders, while successive Byzantine emperors continuously repaired towers and gates to maintain defensive effectiveness.
3. 1442–1453Land walls of Constantinople · ConstantinopleIn the 1440s Constantine XI organized wall repairs and moat clearing, but the garrison numbered only about seven thousand. In 1453, sustained Ottoman cannon fire caused the walls near the Kerkoporta to collapse, and the defenses finally fell.